[SI-LIST] Re: PCB size Vs thickness

D. -- Thickness is usually determined by impedance design constraints
and number of layers - the height of the dielectric being part of that.
But, aside from that, other things come to mind like:

- through hole components and standard lead lengths,=20
- edge fingers, if any,
- aspect ratio of drilled holes (if you have small hole requirements,
like for a FBGA breakout)
- simple cost (more dielectric material =3D more cost)

Smallest finished hole sizes for .062in panels are in the 8mil
neighborhood, and increase for increasing thickness.  I don't think
warpage and board thickness are related.  As long as you have a balanced
construction with an even number of layers.

You mention an 18in X 12in board.  I would recommend that you optimize
your board size if possible to a convenient panel size.  The board shops
typically need a 0.75in to 1.0in border for resin flash, clamping and
racking.  So, a 16in X 12in board size would be the maximum you could
fit on a 18in X 12in panel (which is a standard size in many resin
systems).  Check with your board supplier and ask what the standard
panel sizes he uses for the resin system you've chosen.  Some board
shops have a max panel size they can accommodate because of machine
requirements (i.e. their lam press, tank size, etc.).

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of D.Rajasekar
Sent: Wednesday, January 28, 2004 5:30 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] PCB size Vs thickness


HI all,

I need some guidence on deciding PCB thickness for 18" X 12"
board.

Since there is not much requirements on No.of routing layers & power
layers, i am more considerable to the mechanical aspects of the board
(like warpage,aspect ratio,etc.,).

can some point me the recommended pcb thickness for proposed pcb size
or vice versa? Where can i get those information?

Thanks,
-D.RAJASEKAR

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